The present invention relates generally to apparatus for correction of craniofacial abnormalities, and more particularly to apparatus for affixation to maxillary or mandibular bones to effect distraction of the bones relative to a fracture or osteotomy.
Various developmental disorders of the human skull result in craniofacial abnormalities in which certain bones fail to grow in proper proportion to other bones, or in which certain bones fuse prematurely, causing malformation of the midface or mandible. It is known to correct such abnormalities by separating the bones through osteotomy or fracture, and then slowly distracting the bones relative to each other, thereby inducing bone growth at the separation line. As the bones are distracted, the newly formed bone at the growth surfaces adjacent the separation fills in the increasing gap between the bones. By this method, the midface of the cranium can be advanced forward, or the mandible can be lengthened, for example.
Apparatus for effecting distraction can involve two affixation members, in which each affixation member is temporarily affixed to the bone on opposite sides of the osteotomy, such as by bone screws, and a screw drive member that threadedly engages at least one of the affixation members. By rotating the screw drive member incrementally and periodically, the two affixation members are driven apart, and hence the bones on either side of the osteotomy are distracted relative to the location of the osteotomy. Typically, after the desired amount of distraction is achieved and the new bone growth is sufficiently consolidated, the distraction apparatus is removed.
While the distraction apparatus is in place, the screw drive member must be accessed periodically, typically via the oral cavity, so that a driver can be engaged with the screw drive member to apply torque thereto. Often the location and orientation of the distraction apparatus are such that access to the driven end of the screw drive member is difficult or awkward. To address this problem, universal joints have been used to permit alignment of the driving end of the driver with the driven end of the screw drive member of the distraction apparatus, while permitting the handle of the driver to be oriented at a convenient angle, often outside the oral cavity. Such universal joints can be bulky and do not always provide the desired degree of angular adjustment between the handle of the driver and the driving end of the driver.
It would be advantageous to provide an improved distractor apparatus having a driven member that is more easily accessed by an external driver through the oral cavity. The present invention, an embodiment of which is described below with reference to the drawings, provides this and other advantages.
In accordance with one aspect of the present invention, a bone distractor is provided for distracting bone on opposite sides of an osteotomy of the bone. The bone distractor includes a first affixation member for affixation to the bone on one side of the osteotomy, and a second affixation member for affixation to the bone on another side of the osteotomy. A screw means has a rotatable member that engages the first and second affixation members for distracting the first and second affixation members relative to each other in response to rotation of the rotatable member. An extension has means for removably connecting the extension to the rotatable member of the screw means and for imparting torque to the rotatable member when connected thereto and the extension is rotated.
According to another aspect of the present invention, the extension includes a flexible shaft capable of bending elastically while imparting torque.
It is an object of the present invention to provide an improved bone distractor that is readily accessible for incremental distraction while emplaced in a patient.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.